1. Field of the Invention
This invention relates to the storage of digital information, and more particularly to a miniature disk drive and associated circuitry for storage of digital information on a rotating disk.
2. Description of Prior Art
As computerized devices have been reduced in size over the years, the demand for smaller disk drives has correspondingly increased to keep pace with the reduced sized computing devices. One hard disk drive in the prior art, which includes a 3.5" rigid disk, is described in U.S. Pat. No. 4,568,988 issued Feb. 4, 1986 to McGinlay et al. This patent was reexamined, resulting in the issuance of Reexamination Certificate B1 4,568,988, issued Nov. 29, 1988. McGinlay et al. describe a 3.5" Winchester disk drive which utilizes a disk having a diameter in the range of 85-100 mm. in diameter, with a recording density of 600 tracks per inch, utilizes open loop servo positioning system and reports a storage capacity in excess of 5 megabytes per disk when formatted. McGinlay et al. also disclose the use of a rotary actuator which is driven by a stepper motor through a band.
A further reduction in size of computer equipment lead to the development of a 2.5" form factor rigid disk drive. An example of such a disk drive is illustrated in U.S. Pat. No. 4,933,785 issued Jun. 12, 1990 to Morehouse et al. The rigid disk drive disclosed in Morehouse et al. used two rigid disks, each having a diameter of about 2.5" and utilized a rotary actuator for positioning magnetic recording heads above the tracks of the disks. The "footprint" (width by length measurement) of the drive described in the above-noted Morehouse et al. patent was described as being 2.8".times.4.3". That is, the housing used to enclose the rigid disk drive was 2.8" wide and 4.3" long. A rigid disk drive of this size is generally applicable to computers having a size of 8.5".times.11".times.1". As computers become smaller, such as, for example, a "palm top", "hand held" or "pocket" size, it is necessary to provide a rigid disk-drive which is smaller than either of the foregoing described drives.